Speeds of central processing units (CPU) continue to increase causing computer manufacturers to incorporate them into their products in order to remain competitive. To take advantage of the faster CPUs, graphic controllers and memory devices also need to improve their performance. Notebook computer users now demand parity of performance with desktop computers and this equivalence need causes two serious problems for notebook manufacturers.
The first problem is that as CPUs get faster they consume more energy and become hot, as do the graphics controller and memory devices. The heat from the CPU and other components cause many problems. Hot notebook computers tend to fail more often than cooler notebook computers. This causes real concern among users, as their notebooks are becoming an essential need in their everyday work. When the notebook becomes too warm to touch, not only is it uncomfortable, but concerns are expressed about possible safety and fire hazards. There is even anecdotal evidence that one notebook melted and stuck to an airline seat food tray after a long flight and another that turned a yellow countertop brown.
Past attempts in solving the heat problem have included adding fans or heat pipes and slowing the processor. Adding a fan not only increases cost, it also takes up space and creates audible noise, which many users find distracting. Heat pipes are symbolically equivalent to water canals. They are able to move heat from one area in the notebook to another through a special channel. They too are costly and consume valuable space. Slowing the CPU can reduce heat but the performance of the CPU suffers equally, which fails to meet the users desire for desktop parity. Even if slowing is performed only during periods of idle activity, often times users want to run their notebooks at full throttle so no heat reduction is achieved. Multimedia applications and games are especially demanding in their need for full CPU performance. No user would want to watch a movie for 2 hours only to find their tabletop scorched from the heat of the notebook.
The other problem arising from faster processors is electromagnetic interference (EMI), which is unwanted radio wave emissions. These emissions cause interference with radios and other electronic devices, especially sensitive electronics found on airplanes. Because of the possible serious consequences, EMI radiation is regulated by governments worldwide and is rigorously enforced. It is becoming an increasingly difficult challenge to meet the regulatory requirements for EMI.
Most efforts to solve the EMI issue on products have been done on a trial and error method of test-fix-test-fix. This approach leads to longer product development cycles and late product introduction, thus keeping the latest technology out of the hands of notebook users. Many times the final EMI solution for a product is a hodgepodge of ferrite beads, metal tape, metal shields, foil wrap and special painted cases. The main difficulty in this approach is ensuring consistent EMI shielding to meet the government requirements when mass-producing products and encountering many variations in the different components.
International patent publication WO 97/12313 discloses a method of heat dissipation in a notebook computer by providing for a thermoplate in the lid assembly along with the electronic modules of the notebook. The thermoplate is attached directly to the back of the printed circuit assembly (PCA). The electronic modules themselves are not attached directly to the thermoplate. The electronic modules are facing the LCD panel. The heat from the electronic modules is transmitted to the circuit board through a high thermal resistance created by the PCA. The disadvantages of this approach are many. The first disadvantage is that all modules' heat is sent to a single reservoir, the thermoplate. However, some electronic modules generate more heat than others and may raise the temperature of these other modules outside of their temperature specification causing them to fail. A second disadvantage is that a thermal insulating layer is required to protect the LCD panel from being overheated from the electronic modules giving off heat from their top surface and a vented airspace is required to remove the heat which weakens EMI containment. A third disadvantage is that there is no seal to reduce EMI from radiating outside the lid assembly. The WO 97/12313 application does not address the difficult aspects of how to manage disparate heat sources to allow for individual thermal attention for each module, partition the electronics of the system, or deal with the EMI issues present in high speed notebook design.